Thanks for the research. At this point, I’m still testing things out, so I’m not doing critical restores (though I am in the process of moving all my family members from Crashplan to Duplicati, so I do hope it is generally reliable). I checked the disk (it was fine), added the disable-filetime-check you suggested in the other thread, and did a database recreate. I’m now running the backup again. It seems to be redoing the entire backup, which is maybe a side-effect of the disable-filetime-check?
I’ll let you know if that resolves the issue, though previous attempts to recreate the DB just had the same problem crop up in the new DB.